(1) Field of the Invention
This invention relates to a bipolar electrochemical cell such as a fuel cell or an electrolytic cell, for instance a chlor-alkali electrolytic cell utilizing an oxygen containing gas depolarized cathode.
(2) Description of the Prior Art
Electrochemical cells containing electrodes separated by a permselective membrane, wherein at least one electrode is a gas diffusion electrode and said cell has means for the supply and discharge of an electrochemically active substance in the gaseous state, are well known in the art. Gas diffusion electrodes are used in many electrochemical power sources, for instance metal air cells, methanol air cells, and other types of fuel cells. Ordinarily, one side of the gas diffusion electrode is in contact with a gas phase (for instance the air space in a metal air cell or the hydrogen space in a hydrogen air cell) and the other side is exposed to an electrolyte phase. In bipolar cells, an electrical contact is provided between the electrodes in adjacent units of the bipolar electrochemical cell. In the prior art it has been difficult to provide durable electrical connections between a gas diffusion electrode of one unit of a bipolar cell and the electrode of an adjacent unit of a bipolar cell.
The term gas diffusion or gas depolarized electrode generally refers to a complete electrode in the sense that the electrode is capable of functioning so as to provide a reaction site for a combination of a gaseous substance supplied to one side of the electrode and an electrolyte supplied to the opposite side of the electrode, the reaction taking place within the electrode. Gas diffusion electrodes are generally porous to a gas phase on one side of the electrode and porous to a liquid electrolyte phase on the opposite side of the electrode.
Gas diffusion electrodes for use in electrochemical cells are disclosed in U.S. Pat. No. 4,486,276 wherein an oxygen containing gas is disclosed as contacting a gas diffusion cathode in an electrochemical cell for the electrolysis of an alkali metal chloride. The gas diffusion cathode is fed an oxygen containing gas to eliminate the formation of hydrogen at the cathode during the electrolysis. Gas diffusion electrodes are also disclosed in U.S. Pat. No. 4,271,003.
A bipolar electrolytic cell is disclosed in U.S. Pat. No. 4,279,731 wherein the anode and cathode of said electrolytic cell are separated by a series of baffles distributed along the entire width of the electrode compartment. Said baffles are inclined alternately in different directions with respect to the vertical plane normal to the surface of the cell separator and electrode and define a substantially vertical flow channel for the electrolyte. The electrodes disclosed can be composed of particulate materials which are bonded utilizing a bonding agent but there is no indication that such electrodes are gas diffusion or gas depolarized electrodes.
In U.S. Pat. No. 3,242,059 a process is disclosed for the production of chlorine and caustic soda in a bipolar electrolysis cell wherein neighboring cells are spaced apart by corrugated titanium sheets which also act as current connections between the adjacent cell units of the bipolar electrolytic cell. The corrugated titanium sheets provide anode compartments and cathode compartments in connection with the anode and cathode of adjacent electrolytic cell units. Thus opposite sides of each corrugated sheet define, with the electrodes, compartments for the anolyte and the catholyte liquids of the cell. The anodes and cathodes are of titanium coated with platium.
In none of these references is the novel electrical connector for a bipolar electrolytic cell disclosed wherein said bipolar cell unit has at least one gas diffusion or gas depolarized electrode. A novel electrochemical cell is disclosed herein containing an interspace between positive and negative electrodes. The interspace is divided by said novel connector so as to serve as both a gas space and an electrolyte space.